running more than one server with one IP address

[Bart Silverstrim]

On Aug 28, 2005, at 2:28 PM, David Banning wrote:

> Is it possible to run more than one server(machine) with one IP
> address? I have so many different server-applications running on my 
> machine I
> would like to divide them up.
>
> Maybe using one machine email only, or use one for certain websites,
> and another for other websites. This would also allow me to take-down
> one machines for maintenance when necessary, or use one machine for
> more troubleshooting.
>
> Wondering if someone could even direct me to the terminology that I am
> looking for so I can google it.

The only way I know of doing this is if you have one externally visible 
IP and you're trying to break up services among systems on the internal 
network.  On your router, you'd use port forwarding to redirect 
individual ports to each machine inside your network; i.e., tell the 
router to forward port 25 to your SMTP server, port 80 to your internal 
web server, and port 22 to your internal SSH server whenever requests 
to those port hit IP WWW.XXX.YYY.ZZZ.

I would suppose you'd google for information about NAT and port 
forwarding on routers.

If you try this with an internal system, you're probably going to run 
into issues with ARP routing and collisions.  You'd have to place your 
machines in their own VLAN and have one "internal IP" assigned to the 
interface and still use some kind of redirection to the VLAN 
servers...that's quite a bit of work for most setups, though.

You might be better off messing with your internal DNS so people can 
just go to www.mynetwork.com or smtp.mynetwork.com and have your DNS 
server hand out the proper IP of your server(s).